Over Billing!

As my contract came to an end, I went into my app and selected a new contract for £57 per month. My following bill was £114, so I joined the webchat to enquire why. After 5hrs, I was told something hadn't gone through their end and they couldn't give me that deal now. When arguing my point that it wasn't my fault their end had messed up and I had a contract stating £57, they then agreed to keep to this. I was told I had to agree to a £79 a month contract and a rolling discount would be applied each month to bring it down to £57. I was skeptical, but after being told I would receive new documents to that effect within 24hrs, I waited. Lo and behold, another contract with £79 per month appeared. 2hr more on webchat and I was reasurred that the next bill would be correct. April's bill is £140! I phoned Virgin, and was told that there is no record of prior agreements on my account and I would have to go on webchat again, as it was they who agreed it. So, I am facing losing more hours of my life arguing again, plus demanding refunds, and if course it is now over 14 days so cannot cancel without a hefty penalty! I am so disappointed 😥